The instant invention relates to electromagnetic shielding fabrics, and more particularly to an electromagnetic shielding fabric formed entirely of previously silver-coated synthetic yarns.
It is well known that exposure to long term or acute electromagnetic radiation can have undesirable effects on human tissue, and furthermore, it is also known that electromagnetic radiation can interfere with certain bio-electronic devices, such as pacemakers, which are essential to the daily lives of affected people. The recent proliferation of electronic devices, such as cell phones, and computer equipment, that emit low levels of electromagnetic radiation, or interference, has significantly increased the problem and created a need for everyday shielding garments. In this regard, a variety of electromagnetic shielding fabrics, and garments formed therefrom, have heretofore been known in the art. The previously known EMI shielding fabric constructions can be divided into three basic categories: (1) textile fabrics which are coated with a metallic coating after weaving or knitting of the fabric (see PCT Publication No. WO 92/13352, U.S. Pat. No. 4,572,960 and U.S. Pat. No. 5,275,861); (2) textile fabrics which are primarily formed with natural fibers and include selectively placed conductive yarns (see PCT Publication No. WO95/30229, U.S. Pat. No. 5,569,877, and U.S. Pat. No. 3,164,840; and (3) textile fabrics formed from yarns containing metallic fibers or strands (See U.S. Pat. No. 5,103,504).
While each of the above-noted constructions provides effective shielding characteristics, there are distinct disadvantages to each construction. In general, metal-coated fabrics are not flexible enough to form everyday wear garments. Still further metal-coated fabrics are subject to surface wear, and a subsequent decrease in conductivity and shielding as breaks are formed in the metal coating when the fabric is bent. With specific regard to WO 92/13352, the entire textile fabric is after-coated with copper. Copper, in general, is not a practical coating material for garments because copper oxidizes into copper oxide which is non-conductive, and furthermore, the copper oxide is known to leave a green residue on the wearer. With regard to textile fabrics having selectively placed conductive yarns, these fabrics generally do not provide a sufficient level of conductivity to provide high-level shielding capabilities. Finally, with regard to fabrics having yarns containing metallic fibers, the metallic fibers are usually located within the interior of the yarn to prevent contact with the wearer. However, because the conductive elements of the yarns are internalized, conductivity is not continuous from yarn to yarn, and therefore the fabrics formed from these yarns also do not provide a sufficient level of conductivity to provide high level shielding capabilities.
The instant invention provides a electromagnetic shielding fabric which is effective for shielding a person from electromagnetic radiation having a power density of up to 10 mw/cm.sup.2, and which is also highly flexible and non-irritating to the skin of the wearer. More specifically, an electromagnetic shielding fabric is formed entirely from a plurality of synthetic fiber yarns which have been previously coated with silver. The preferred yarn structure comprises silver-coated nylon yarns. However, other synthetic yarns, such as acrylic yarns and polyester yarns can also be effectively used as a base for the silver-coating process. The silver content of the silver-coated synthetic yarn is preferably not less than 20% by weight, and the conductivity of the silver-coated yarn is preferably not less than 1.2 ohms/cm. The silver-coated synthetic yarns are preferably formed into a textile material by means of a warp-knitting method which interlocks all of the yarns in a continuous chain stitch. The resulting fabric is thus formed substantially entirely of the conductive silver-coated yarns thereby providing superior conductivity and electromagnetic shielding capability. Because of the resulting flexibility and suppleness of the silver-coated nylon fabric, the fabric can be fashioned into a variety of everyday wear garments, including shirts, pants, hoods, hats, bed sheets, blankets and curtains.
Accordingly, among the objects of the instant invention are: the provision of an EMI shielding fabric with a high-level of shielding capability that is also highly flexible, non-irritating to the skin and also bactericidal; the provision of a shielding fabric fashioned entirely from silver-coated nylon yarns wherein the silver content of the yarns is not less than 20% by weight; the provision of a shielding fabric fashioned entirely from silver-coated nylon yarns wherein the conductivity of the yarns is not less than 1.2 ohms/cm; the provision of EMI shielding garments fashioned entirely from silver-coated nylon yarns wherein the resulting fabric can be fashioned into a variety of everyday wear garments, including shirts, pants, hoods, hats, bed sheets, blankets and curtains.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.